I don't think so. This is why I asked you to give me a test case. Yet, you have not. Try a test case adding children in the reverse order (start with index 5 and then end with index 0), and see if they show up in the right order or not. Then, attach the test case.

In any case, I'm going to close this ticket. It's true that addChild() behaves differently now when passed illegal arguments, but the new behavior of throwing an exception (albeit perhaps a hard to understand exception) is more in line with dojo's principles.

In many cases, a _Container will have a child nodes map. This, or an index on the child itself, could be used to insert children at the correct position. The downside is that this introduces state. But I suspect some state will be used anyway.